function [ d ] = distance( x1,x2,y1,y2,z1,z2 )
%DISTANCE Summary of this function goes here
%   Detailed explanation goes here
    d = sqrt(   (x1-x2)*(x1-x2)    + ...
                (y1-y2)*(y1-y2)    + ...
                (z1-z2)*(z1-z2)           );
end
